In countries where there is one dominant party and a divided opposition, the proportional seats may be essential for allowing an effective opposition.

In the run up to the election, various organizations are conducting opinion polls to gauge voting intentions for the available proportional seats.

It wanted to reform the electoral law so that an amount of the seats proportional to the rate of abstention would be left empty.

After losing also his proportional seat in 2005, he was elected to the House of Councillors for the first time in 2007.

Parties had to receive at least 4% of the national vote to win any of the proportional seats, which were distributed using the largest remainder method.

The constituency seats won by each coalition would not reduce the number of proportional seats they received.

The parties were attributed a number of seats proportional to the number of votes they received.

Toranosuke Katayama won the party's only proportional seat in this election.

In the 2005 elections the party received 20% of the vote in the national voting for the proportional seats, putting it in first place.

The number of proportional seats increased from 400 to 484, while the 242 electoral districts were maintained.